function dy=zhuiji2(t,y)
Vdd=450;
Vdj=135;
k1=(y(2)-y(4))/(y(1)-y(3)+eps);
k2=-1/k1;
dy=zeros(4,1);
dy(1)=Vdd/sqrt(1+k1^2);
dy(2)=Vdd*k1/sqrt(1+k1^2);
dy(3)=Vdj/sqrt(1+k2^2);
dy(4)=Vdj*k2/sqrt(1+k2^2);
